This invention relates to a unique glove structure and to the apparatus and method for making the glove structure.
For many years, surgical gloves and non-supported household gloves have been made by a process which involves dipping a smooth surfaced porcelain or aluminum glove form fashioned to resemble, to a large degree, the human hand into a solution of latex coagulant (usually a solution of calcium nitrate in alcohol), drying the latex coagulant and then immersing the form into a latex compound. After depositing the layer of latex compound on the forms, the forms are usually rotated throughout the period of time necessary for the coagulant to react with and gel the latex film. This rotation equalizes any wet latex runs and assures a more uniform overall guage in the finished glove. After the film is gelled, it is leached with water or steam to remove any water soluble materials from the deposit, dried, vulcanized and stripped from the glove as a finished glove.
Glove forms historically have been shaped to resemble, as nearly as possible, the human hand. This is to say, the glove forms available on the market generally resemble a hand, especially in cross section, with the fingers and palm portions being round or elliptical in cross-section and the base or cuff portion of the form being generally round.
Although the finished rubber or plastic glove conventionally made on such forms resembles in overall contour, the mold on which it was dipped, it is not usually economically feasible to market a glove which is oriented precisely as dipped. This is because removal of the glove from the form is usually effected by pulling the glove off of the form cuff end first, fingertips last, thereby reversing the glove. Since the gloves are normally thin and extremely pliable, reversing them does not substantially alter their functionality. Consequently, most thin dipped gloves marketed today are reversed from the way they were dipped. This concession to the economics of manufacture is harmful to the serviceability of the glove in a number of ways.
It has been found that elastomers age best in the static state, that is to say, all other factors being equal, a latex rubber article which is maintained exactly as molded or dipped will age better than a similar article which is stretched or distorted. A reversed glove presents certain areas which are stressed because of the inherent "memory" of rubber or plastic. These areas usually are manifested as sharp creases in the film. Viewing a glove in repose, these areas are usually in the crotches and along the sides of the gloves. Gloves which are especially sensitive to aging influences, such as natural rubber, cis polyisoprene and blends thereof will quickly crack and generally degrade in the areas outlined when exposed to the deleterious effects of oxygen, ozone or ultraviolet radiation, or to any combinations of these. Consequently, it is desirable to avoid any such sharp creases in the finished glove product if at all possible.
Another significant disadvantage of the glove structure made in accordance with conventional manufacturing techniques is the difficulty of donning such gloves. Since these gloves are primarily intended to conform closely to the skin of the wearer, the glove is normally smaller than the wearer's hand and must, therefore, be stretched in order to place the glove on the hand. Conventionally formed gloves having round or elliptically shaped finger compartments have the inherent disadvantage that air will become entrapped in the finger compartments during insertion of a wearer's hand. This characteristic impedes the donning of the glove, in that venting of the entrapped air is extremely difficult.
In addition to the disadvantages associated with the glove product produced by conventional glove-making techniques, set forth below are a number of disadvantages associated with the use of the equipment itself:
1. Because the glove forms are generally shaped in the configuration of a human hand, there is a relatively large surface area on the form which is parallel to the liquid interface during dipping. Surfaces parallel to the liquid tend to trap air during dipping causing voids or blisters in the film. These relatively large surfaces parallel to the liquid interface also slow the dipping time and thereby increases the overall machine time. Customarily, these surfaces are so prone to air entrapment the dip mechanism must be automatically sequenced to enter the liquids (coagulant and latex) at much reduced speeds in the areas of the fingertips and crotches, the remainder of the glove being dipped much faster.
2. Because gloves of the type contemplated by the present invention are normally provided in different sizes, it therefore must follow that the glove-making forms will be of different sizes. Therefore, the latex displacement within the dipping tank will vary substantially from one size form to another. This variation in dipping levels created by the different sized forms is considered to be very undesirable during a manufacturing operation.
3. The rounded forms which conform generally to the contour of the human hand are relatively bulky forms and therefore have the disadvantages of (a) relatively high mold cost, (b) less efficient and non-uniform heat transfer (since these forms are conventionally hollow), (c) greatly reduced machine capacity occasioned by the necessity to utilize many closely spaced forms during a single dipping operation, and (d) the rounded forms, because of their bulk, are relatively heavy in weight.
An additional factor which has long been a problem in the manufacture of gloves by conventional techniques is the difficulty in stripping, or otherwise removing, the cured glove product from the glove-making form. Since conventional forms have been, as stated above, constructed to conform generally to the overall contour of a human hand, the elastomeric material deposited on the form has a convex configuration which tends to cling tightly to the form and impedes the stripping operation. This is a very important step in the overall glove-making procedure in that it has conventionally been a hand operation and, therefore, contributes greatly to the overall cost of the glove product. Therefore, improved techniques for stripping and handling the finished glove products has long been sought.